Thoughts on Watering Plants

What is the best watering frequency for watering to use for my system? In my 30 plus years of working in the green industry, this, or some derivation, is the most asked question I hear. It is also the hardest one to answer. There is absolutely no easy response, but only one right one: when the plant needs it. Both the frequency of water applications and, to a lesser extent, the amount of water to apply, are dependent on many outside variables that further complicate the issue, thus requiring the grower to maintain an ‘eyes on’ approach in his or her growing techniques.

By : Geary Coogler, BSc. Hort

This is the one area in the growing process that makes or breaks a grower. Once we moved out of a natural setting into one of our own design, and began demanding the best performance from those crops we produce, we opened the ‘Pandora’s Box’ of growing.
We fundamentally changed water relations between the plant, the medium, and the grower. To fix this problem, the industry has developed a wide variety of mediums and systems that work well with the change.  The question ‘Which one is right for you’ is answered entirely on the type grower you are. Understanding how the pieces act when they come together will give you an indication in what method should work best with your style. We modify our approach to watering to adjust for all the variables our plants may see that are unique to our growing situation, and we will achieve the best results possible. The one variable we cannot adjust for is a grower that does not adapt his or her growing techniques, or design his/her production system around those limitations.

THE GROWTH TETAHEDRON

Let’s begin our look at watering by accepting a small fact: The successful completion of a plant crop is predicated on the successful implementation of the growth Tetrahedron (see Figure 1-1).

Figure 1-1 Growth Tetrahedron

The tetrahedron has as its sides the 4 primary components of achieving growth. Each side is equal in importance and must be optimized to fit with the other sides. As you can see the base of the pyramid is water (as a solution or pure) because it exists in all the sides as well. The Plant Selection will determine both the root environment (and consequentially the system or medium that will be used), and the top environment that will be needed (sides 2, 3 and 4). It takes all four sides to make the tetrahedron and each determines the limits of the others.

The plant or crop is the first side and the first decision. Based on what you want to grow will determine how to grow it; on which root environment and top environment to use is predicated on the chosen plant. In addition, choices are made based on the grower’s knowledge of the system, the crop, strengths and weaknesses, and the remaining two sides. It makes no sense to attempt tomatoes if the environment does not have sufficient light. It makes equally little sense to grow Orchids when the water solution is scarce. While lettuce may be grown successfully in peat or coco, it can be grown as well in an NFT system while decreasing the time, costs, and environmental area it occupies. Just because you can grow leaf lettuce in your grow room, does not mean you can grow head lettuce successfully unless you can drop the temperature in the room to cooler levels. Choose your plant carefully, both type and variety, as all are different and will respond different.